From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 6C99AE6FE52 for ; Fri, 22 Sep 2023 16:00:48 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S230500AbjIVQAw (ORCPT ); Fri, 22 Sep 2023 12:00:52 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:55296 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S230212AbjIVQAv (ORCPT ); Fri, 22 Sep 2023 12:00:51 -0400 Received: from smtp.kernel.org (relay.kernel.org [52.25.139.140]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 9D47C102 for ; Fri, 22 Sep 2023 09:00:45 -0700 (PDT) Received: by smtp.kernel.org (Postfix) with ESMTPSA id E2FCAC433C8; Fri, 22 Sep 2023 16:00:42 +0000 (UTC) Date: Fri, 22 Sep 2023 17:00:40 +0100 From: Catalin Marinas To: Shameer Kolothum Cc: kvmarm@lists.linux.dev, kvm@vger.kernel.org, linux-arm-kernel@lists.infradead.org, maz@kernel.org, will@kernel.org, oliver.upton@linux.dev, james.morse@arm.com, suzuki.poulose@arm.com, yuzenghui@huawei.com, zhukeqian1@huawei.com, jonathan.cameron@huawei.com, linuxarm@huawei.com Subject: Re: [RFC PATCH v2 6/8] KVM: arm64: Only write protect selected PTE Message-ID: References: <20230825093528.1637-1-shameerali.kolothum.thodi@huawei.com> <20230825093528.1637-7-shameerali.kolothum.thodi@huawei.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20230825093528.1637-7-shameerali.kolothum.thodi@huawei.com> Precedence: bulk List-ID: X-Mailing-List: kvm@vger.kernel.org On Fri, Aug 25, 2023 at 10:35:26AM +0100, Shameer Kolothum wrote: > From: Keqian Zhu > > This function write protects all PTEs between the ffs and fls of mask. > There may be unset bits between this range. It works well under pure > software dirty log, as software dirty log is not working during this > process. > > But it will unexpectly clear dirty status of PTE when hardware dirty > log is enabled. So change it to only write protect selected PTE. Ah, I did wonder about losing the dirty status. The equivalent to S1 would be for kvm_pgtable_stage2_wrprotect() to set a software dirty bit. I'm only superficially familiar with how KVM does dirty tracking for live migration. Does it need to first write-protect the pages and disable DBM? Is DBM re-enabled later? Or does stage2_wp_range() with your patches leave the DBM on? If the latter, the 'wp' aspect is a bit confusing since DBM basically means writeable (and maybe clean). So better to have something like stage2_clean_range(). -- Catalin